Using FLC mode in light piston aircraft - in descent?

[RussR]

I regularly fly a faster light GA piston plane with a G1000 and GFC 700 autopilot. I routinely use FLC mode in climb and it does a great job.

But in descent, I either use VNAV mode or VSI hold, depending on what I'm trying to accomplish.

But since I really like using FLC in a climb, am I missing some great opportunity by not using it in a descent as well?

I tried it yesterday, and while it did a fine job maintaining the speed I set, I didn't think it was very useful as the descent rate varied with altitude (since it locks onto an IAS) and obviously didn't follow a vertical path either. (Note that this airplane does not have autothrottles.) It did, however, keep me out of the yellow arc which was great because it got bumpy.

For those of you flying bigger, fancier equipment, do you use FLC in a descent? When/under what conditions? And anyone using it in a piston airplane (effectively meaning "at piston altitudes")?

 

[oskrypuch]

Normal descent mode from cruise is an intelligent VNAV mode, that is driven by the FMC setup which allows for prevailing wind at various altitudes and the M/IAS rollover at around FL290, and is tuned for efficiency/speed by a factor called Cost Index. It computes a VNAV path and VNAV speed and executes it.

FLCH (LVLCHG) mode in airliners provides envelope protection, and when not in VNAV it is either recommended or required for operations, most commonly it would be used below 10,000ft when maneuvering on vectors for the approach. VS mode is used only for small altitude adjustments, or where a short targeted descent is required.

No reason not to use Garmin's FLC mode in descent, if it provides an operational advantage for you. The envelope protection is more important in ascent, but useful in descent as well.

* Orest

 

[jordane93]

I use LVL CHG whenever VNAV isn’t appropriate. If we’re getting vectored off the STAR and if it’s more than a 2000ft change in altitude, I’ll use it. Generally below 10K. If ATC gives me an altitude change of only 1000ft, it doesn’t make sense for me to use LVL CHG because I don’t need the autothrottles to command an idle descent and then rev back up for 1000ft. So instead I’ll use V/S. VNAV is the preferred method for climbs for my airplane and my airline.